Ashman is the lyricist behind Disney classics Aladdin, Beauty and the Beast and The Little Mermaid. He was also the creator of musical Little Shop of Horrors.
"As a lyricist, the last great place to do musicals is in animation," Ashman says in a trailer for the film that was released on Thursday.
Howard, from director Don Hahn, will feature archival footage, personal films and photographs and interviews with his friends and family.
"You may not know his name, but you sure know Howard Ashman's music," Hahn said in a statement.
"He's one of the greatest storytellers of the twentieth century who helped to revitalize the American musical and re-energize Disney Animation. He left us a songbook that still lives on in us today, yet his personal story has never been fully told until now," he continued.
Howard first premiered at the 2018 Tribeca Film Festival. The documentary contains interviews with Ashman's longtime musical collaborator Alan Menken, his partner Bill Lauch, Jodie Benson of The Little Mermaid, Paige O'Hara of Beauty and the Beast and his sister, Sarah Gillespie.